2006-12-12

I don't have time to really think too hard about this story, but it is making the rounds, so I'll at least acknowledge it. Some NCAR simulations now predict essentially no late-summer ice in the Arctic by 2040. See the story at BBC [LINK] or at Nature [LINK]. The actual paper is in Geophysical Research Letters [doi:10.1029/2006GL028024].

What does this mean? Well, I haven't had a chance to look closely at the paper, but I have some first impressions. I did get a sneak-peek of these results this summer, and at the same time was introduced to some of the details of the sea-ice model used in CCSM (NCAR's climate model), so maybe I'll be able to say something halfway meaningful. The paper itself does not predict an ice-free Arctic in 2040, so let's just get that out of the way. This paper is really about the possibility of abrupt decreases in sea-ice in a changing climate, and the current generation of climate models suggest a real possibility of large reductions in perennial ice coverage in the first half of the 21st century. The main focus is a set of CCSM simulations using one of the emissions scenarios from IPCC. They also take a look at some of the results from other IPCC models. The CCSM always has what the authors call "abrupt reductions" in Arctic ice, and several of the other models also show large reductions.

I am willing to accept these results, but I think some skepticism has to be exercised still. First off, this is a GRL paper, which is a journal of short, usually preliminary, work focusing on "sexy" results. The peer-review process for GRL is sometimes thought to be a little lax, and sometimes the quality of the work is questionable. That does not seem to be an issue for this paper; the CCSM is a respected climate model, the authors are top-notch climate scientists, and this work is presented well. That said, this is not the last word on this project; I'm sure that the authors are doing more detailed work and are planning a longer, more careful analysis for another journal (e.g., Journal of Climate, Climate Dynamics). The best thing that could do would be to better quantify what "abrupt changes" really are, and the physical processes that trigger them, which is a big open question in this paper. They say the abrupt changes are driven by thermodynamics, but don't really present evidence of this; I assume they mean that wind patterns/ocean currents are changing to just move ice out of the Arctic, but it is not explained. The other thing to keep in mind is that even in the current generation climate models, the sea-ice models are fairly crude. I don't mean that in a bad way, the people working on these models are doing the best they can. Ice processes are quite complicated, and to properly model sea-ice, much like "properly" modeling clouds, the simulations need to be run in much higher resolutions. That kind of resolution is too expensive right now, and even if the resources were there, it would be a tough sell to dedicate it to the sea-ice component rather than better atmospheric and oceanic components. This particular climate model is known to be fairly sensitive, and when it gets knocked out of equilibrium, the sea-ice is one of the things known to respond fairly erradically. So while I think the CCSM, and several other high-end climate models, can get a lot of important changes correct, we still can't trust the details of these fully coupled simulations. My interpretation is then something like this: in the near future (50 years), it is likely that rapid reductions in perennial Arctic sea-ice will be observed, associated with (but not well-correlated with) increasing atmospheric greenhouse gases.

2006-12-07

A small story, ultimately of no consequence, suggesting the "need" for a Nobel Prize for the Environment: LINK.

Funny as it may sound, I don't think it would be a very good idea to add such a prize. I would like to see more earth scientists honored for their contributions to understanding physics, chemistry, and dynamical system, but the Nobel prizes are so high profile, and climate change such a charged issue, I think such a prize would be politicized immediately. That would sully the award, because there would always be questions about why people get the prize. Not only that, but it would be difficult to separate scientific achievment in understanding the environment from conservation of the environment, which is more social science or economics or political or who knows what. If conservation groups tended to be awarded the prize, then earth scientists would be even less likely to be honored, since they wouldn't get the environment prize and they'd usually be excluded from the physics or chemistry prizes.

There is also the issue of the maturity of the fields of meteorology, oceanography, climate dynamics, environmental sciences, and such. While those of us in the field could come up with a list of deserving people, it would be difficult after a few years to say with confidence that a person(s) have made a lasting positive contribution. This comes up in the other science prizes when people complain that awardees get the award decades after the work, but the defense is that it takes that long to figure out what work needs to be honored. We don't really have very many decades of work to choose from (of course, excluding the early pioneers like Bjerknes, Charney, Richardson, Ekman, von Neuman, and many other dead folks).

2006-12-05

Today's little tidbit is a short news story about a Journal of Climate paper [LINK]. The paper is about a climate simulation that includes an ocean (and presumably a carbon cycle model). The bottom line is that they think they have a credible southern hemisphere atmospheric circulation, with then drives a realistic Antarctic circumpolar current. If you have never done so, go get a globe and look at it from the "bottom," so you are looking right at the south pole; notice that there is a ring of water around Antarctica. That's the only place where that happens, and it makes a big difference to the world's climate. Anyway, they say that as the winds around Antarctica move south, they change the uptake of carbon dioxide into the ocean, which partially offsets the climate change associated with the anthropogenic greenhouse effect. That's good! Unfortunately, it also accelerates sea level rise (by pumping heat into the ocean, raising the temperature faster) and ocean acidification (which might feed back onto the carbon cycle if critters start dying off). So there you go. Maybe I'll try to tap Nikki for more nuianced insight, since this is closely related to her work.

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While the news reported and linked from this blog belongs to the authors of that material, the perspective included here is entirely my opinion. Any original analysis or figures should be considered preliminary at best, and may be shared freely provided notification is sent to me via this blog's comments or through other electronic communication. None of the content here is supported in any way by my employer, funding agencies, or any branch of the United States government. Enjoy.